The present invention relates to a rivetless floating anchor nut assembly including a nut member and a basket member, to the basket member per se and to a flaring tool for use in affixing the basket member and hence the anchor nut assembly to a workpiece.
Floating anchor nut assemblies have been known and used for many years, each such assembly including a nut member and a basket member affixable to a workpiece by rivets passing through mounting holes in the basket member and the workpiece. An example of such a prior art assembly is found in Swanstrom U.S. Pat. No. 2,243,923, granted June 3, 1941. Floating anchor nuts of which that of said Swanstrom patent provides an example are subject to the limitation that edge mounting distances are limited. Furthermore, the rivet holes may provide areas of stress concentration giving rise to fatigue failure. It is therefore desirable to provide a floating anchor nut assembly which does not entail the use of rivets.
It is also desirable for many floating anchor nut applications, that the nut member be replaceable an indefinite number of times.
Gulistan U.S. Pat. No. 3,695,324, granted Oct. 3, 1972, discloses a rivetless floating anchor nut assembly including a nut member which is replaceable an indefinite number of times. As brought out in more detail hereinafter, the device of the Gulistan patent entails a three-piece assembly, including, in addition to the nut member, a basket member of springy or resilient material and an attaching sleeve of malleable material. The Gulistan patent specifically teaches that the resiliency of the basket member and the malleability of the attaching sleeve cannot be combined in a single piece, where nut member replaceability is desired.
It has been found, unexpectedly and unobviously, that the resiliency of the basket member and the malleability of the attaching sleeve of the Gulistan patent can be combined in one piece, namely, a basket member, if the basket member has a hardness in the range of which the lower limit is 34 on the Rockwell C scale and the upper limit is 38 on the Rockwell C Scale, thus eliminating the need for the attaching sleeve of the Gulistan patent as a piece separate from the basket member. Preferably, the basket member is of heat treatable metal, heat treated to have a hardness within said range. Still more preferably, the basket member is heat treated to a uniform hardness in said range. The direct cost saving which is made possible by eliminating the attaching sleeve from the three-piece assembly of the Gulistan patent is a significant advantage of the present invention.
It is therefore an important object of the present invention to provide a rivetless floating anchor nut assembly which has fewer pieces and is thus less costly than the assembly of the Gulistan patent. More particularly, it is an important object to provide a rivetless floating anchor nut assembly which includes a nut member and a basket member wherein the basket member is at the same time sufficiently resilient to enable the nut member to be replaced an indefinite number of times and sufficiently malleable to enable the basket member to be permanently deformed so as to affix the basket member and hence the assembly to a workpiece.
It is a further object to provide a novel and unobvious basket member for use as a component of a rivetless floating anchor nut assembly.
In addition to the direct cost reduction realized by the floating anchor nut assembly of the present invention with respect to the floating anchor nut assembly of the Gulistan patent, a floating anchor nut assembly in accordance with the present invention is considerably lighter in weight than that of the Gulistan patent.
Furthermore, in the anchor nut assembly of the Gulistan patent, the attaching sleeve has a flange of substantial axial thickness at one end, which flange is interposed between confronting surfaces of the basket member and the nut member. The flange of the attaching sleeve contributes to the overall axial extent of the assembly. The present invention, by combining the functions of the basket member and the attaching sleeve of the Gulistan patent in a single basket member, eliminates from the overall axial extent of the assembly the thickness of the flange of the attaching sleeve of the Gulistan patent and enables the use of shorter, lighter and less costly bolts. The saving in bolt weight is likely to be much more significant than the saving in weight of the floating anchor nut assembly per se.
Therefore, further objects of the invention are to provide a floating anchor nut assembly which is substantially lighter in weight than that of the Gulistan patent, to provide a floating anchor nut assembly which is of reduced dimensions with respect to that of the Gulistan patent and to provide floating anchor nut assembly requiring shorter and hence less costly and lighter bolts than are required with the floating anchor nut assembly of the Gulistan patent.